This invention relates to overshot and safety apparatus for retracting a core barrel inner tube assembly and mechanism to decrease the chances of unintended movement of the inner tube assembly outwardly of the drill string which can result in injury to personnel during up-hole drilling (drilling is at a hole angle that is above the horizontal).
During up-hole drilling with wire line equipment, the inner tube assembly can unexpectly move to and through the outer end of the drill string and injure someone. For example, if the inner tube assembly is not properly maintained, it is possible the inner tube assembly can move to the outer end of the drill string in an uncontrolled manner. To stop such outward movement of an inner tube assembly or the like, it is necessary to consider connecting a device such as a xe2x80x9csafety subxe2x80x9d at the outer end portion of the drill sting. A sub is usually a short coupling having male and female thread connections. Such a sub can have a closed end or have a minimum inner diameter portion that is of a small inner diameter than the maximum outer diameter of the outer end portion of the drilling tool that is used in the drill string, for example, a core barrel inner tube assembly or an overshot assembly.
A problem with such a safety sub is that it must be removed from the outer end of a drill string in order to insert a prior art overshot assembly in the drill string preparatory to retrieving a core barrel inner tube assembly when it is filled with core. In removing the sub from the drill string, in order to be able to insert a wire line overshot assembly, the operator is exposed to the open outer end of the drill string through which the drilling tool in the drill string may move outwardly in a dangerous manner whereby the operator is exposed to possible injury when the drilling direction is upwardly. After the overshot assembly is pumped to the inner end of the drill string and then attempting to unlatch (uncouple) the inner tube assembly from its latched condition in the drill string, it is possible to have a mistaken unlatched or a xe2x80x9chung-upxe2x80x9d inner tube assembly whereby the overshot assembly is retracted without the inner tube assembly coupled thereto. Again, the operator is exposed to possible injury from the drilling tool if and when it unexpectly moves out of the outer end of the drill string.
In U.S. Pat. No. 3,120,283 to Braun there is disclosed an underground overshot assembly (see FIGS. 10 and 11) that is fluidly propellable to the bit end of the drill string regardless of the drilling direction. The overshot assembly includes a main body pivotally mounting pulling dogs and a valving subassembly that provides an open fluid bypass channel when being retracted though the drill string.
In order to make improvements in overshot and safety apparatus that is particularly usable in up-hole drilling (a drilling direction above the horizontal), this invention has been made.
The overshot assembly includes a main body mounting pulling dogs for movement between an inner tube assembly coupling position and a release position, an annular seal for forming a fluid seal with the interior of a drill string, an elongated overshot tube joined to the main body and valving mechanism resiliently urged to block axial outward flow through the overshot tube. A safety sub is removably mounted to the outer end portion of the drill string while an overshot adaptor is removably mounted to sub to prevent the overshot assembly moving inwardly of the sub and to retain overshot valving mechanism in an open condition. The overshot adaptor includes valving mechanism to permit fluid to be pumped inwardly through the overshot adaptor and the overshot tube and block fluid flow in the opposite direction, the combination of the overshot assembly and overshot adaptor being axially slidably movable a limited amount relative to the sub. When it is desired to retract an inner tube assembly or other drilling tool, the water swivel is removed from the drill string and a disconnect tool is used to pull the overshot adaptor to extend outwardly in the sub. Now the overshot adaptor is unthreaded from the overshot assembly. Then a wire line adaptor is threaded to the overshot tube to close the outer end thereof and a loading chamber is threaded to the sub and fluid under pressure is pumped into the sub for forcing the overshot assembly inwardly.
One of the objects of this invention is to provide new and novel overshot means for use in up-hole drilling apparatus that is usable in combination with a safety sub to minimize danger when a drill tool is in a drill string during up-hole drilling and the outer end of the drill string is opened. Another object of the invention is to provide new and novel overshot and safety apparatus that is retained at the outer end of a drill string while a bore hole is being drilled. In furtherance of the last mentioned object, it is another object of this invention to provide new and novel adaptor means to cooperate with a safety sub and a new and novel up-hole overshot assembly to retain the overshot assembly adjacent to the outer end of a drill string while permitting fluid under pressure being pumped through the overshot assembly when drilling with a core barrel inner tube assembly. An additional object is to provide new and novel overshot means that is fluidly propellable in a drill string in an upward direction when connected to wire line means and block axial outward fluid flow therethrough when disconnected from such wire line means and not mechanically retained in an unblocked fluid flow position.
For purposes of facilitating the description of the invention, the term xe2x80x9cinnerxe2x80x9d refers to that portion of the drill string, or of the assembly, or an element of the assembly being described when, in its position xe2x80x9cfor usexe2x80x9d in, or on, the drill string is located closer to the drill bit on the drill string (or bottom of the hole being drilled) than any other portion of the apparatus being described, except where the term clearly refers to a transverse circumferential, direction, or diameter of the drill string or other apparatus being described. The term xe2x80x9couterxe2x80x9d refers to that portion of the drill string, or of the assembly, or an element of the assembly being described when, in its position xe2x80x9cfor usexe2x80x9d in, or on, the drill string is located axially more remote from the drill bit on the drill string (or bottom of the hole being drilled) than any other portion of the apparatus being described, except where the term clearly refers to a transverse circumferential, direction, or diameter of the drill string or other apparatus being described.